Brown Fat Present and Active in Adults

Brown adipose tissue, whose function in small mammals is to maintain body temperature, is present in adult humans and becomes more active after mild cold exposure, suggesting that it could be targeted to modulate energy expenditure, according to three studies published in the April 9 issue of the New England Journal of Medicine.

WEDNESDAY, April 8 (HealthDay News) -- Brown adipose tissue, whose function in small mammals is to maintain body temperature, is present in adult humans and becomes more active after mild cold exposure, suggesting that it could be targeted to modulate energy expenditure, according to three studies published in the April 9 issue of the New England Journal of Medicine.

In the first study, Wouter D. van Marken Lichtenbelt, Ph.D., from Maastricht University in the Netherlands, and colleagues examined the activity of brown adipose tissue using radiolabeled fluorodeoxyglucose imaging in 24 healthy young men, where 10 were lean and 14 were overweight or obese. They observed activity in 23 of the men only during mild cold exposure (16 degrees Celsius). The activity was significantly lower in the overweight or obese men.

In the second study, Aaron M. Cypess, M.D., Ph.D., from the Joslin Diabetes Center in Boston, and colleagues used radiolabeled fluorodeoxyglucose imaging in 1,972 patients and found that substantial brown adipose deposits were present in a region from the anterior neck to the thorax, and that more than twice as many women had deposits as men. In the third study, Kirsi A. Virtanen, M.D., Ph.D., from the University of Turku in Finland, and colleagues used radiolabeled fluorodeoxyglucose imaging in five healthy volunteers, which determined that substantial amounts metabolic activity of brown adipose tissue were present.

"The common message from these studies is that brown adipose tissue is present and active in adult humans, and its presence and activity are inversely associated with adiposity and indexes of the metabolic syndrome," Francesco S. Celi, M.D., from the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md., writes in an accompanying editorial.